8 grade the dynamic earth (module e) · 2020. 1. 9. · what landforms can streams create? what do...

Unit 1 Lesson 3 Erosion and

Deposition by Water

8th Grade

The Dynamic Earth (Module E)

Copyright © Houghton Mifflin Harcourt Publishing Company

Flowing water changes Earth’s surface

• Erosion is the process by which sediment and other materials are MOVED from one place to another.• Sediment: tiny grains of broken-down rock.

• Deposition is the process by which eroded material is DROPPED. (usually downstream)

• Happens when pull of gravity is more than force of flowing water or wind

Unit 1 Lesson 3 Erosion and Deposition by Water

Factors that control how much sediment a stream moves -

• 1. Gradient – change in elevation over a certain distance• “Steepness” or “slope”• Steep gradient = more energy to carry soil



• 2. Load - the materials carried by a stream.

• The size of the particles in a stream’s load is affected by the stream’s speed.

• Fast-moving streams = large particles and high erosion rate.

• Slow-moving streams = smaller particles and low erosion rate.



3. Discharge - amount of water that a stream carries

• Increases after large storms and rapid snow melts.

• As a stream’s discharge increases, its erosive energy, speed, and load increase.

• Do the math! Page 31




What landforms can streams create?What do you think? – read pg. 32-33

• channel - the path that a stream follows

• canyons and valleys


• When rivers flood, sediments get deposited over flooded land

• floodplain - flat area formed from many layers of deposited sediment. (Deposition!)

• often very fertile – sediment contains nutrients



• Curves and bends in a stream channel are called meanders.

• Moving water erodes the outside banks and deposits sediment along the inside banks.

• sometimes a meander can be cut off, forming an oxbow lake.

- Water Erosion

• When a stream empties into another body of water, its current slows and it deposits its load.

• delta -fan-shaped pattern of deposited sediment IN WATER



• alluvial fan - fan-shaped deposit that forms ON DRY LAND.



What landforms can streams create?

• What landforms can you identify in the image below? Explain how each type of landform formed.




• Groundwater - water located within the rocks below Earth’s surface

-Acidic groundwater dissolves rock, forms caves

• Sinkhole - circular depression when cave roof collapses

Unit 1 Lesson 3 Erosion and Deposition by WaterLandforms made by groundwater erosion

• Stalactitesand stalagmites -icicle-shaped deposits from water dripping from cracks in cave’s ceiling

• Both waves and currents affect the shoreline (place where land and a body of water meet)


Unit 1 Lesson 3 Erosion and Deposition by WaterErosion and Deposition by the OCEAN


Unit 1 Lesson 3 Erosion and Deposition by WaterWAVES• waves slow down and bend around

headlands (pieces of land that project into the water) as they approach shoreline

• strike headlands with MORE energy (so more erosion)

• Strike betweenheadlands withless energy(so more deposition)

• Currents that travel almost parallel to the shoreline very near shore.

-Caused by waves hitting the shore at an angle.-As sand moves down a beach…


Unit 1 Lesson 3 Erosion and Deposition by WaterLONGSHORE CURRENTS

-upcurrent end iseroded away

-downcurrent end is built up

What forces shape a shoreline?

• What might this beach area look like in the future?




• The rate at which rock erodes depends on the hardness of the rock and the energy of the waves.

• Gentle waves - little erosion, • Strong waves (from storms) - increase rate

of erosion.

• Harder rock slows the rate of erosion -takes more wave energy to break the rock.

• Soft rock erodes more rapidly.


Some landforms made by erosion (p. 36 picture)



• sea cliff - waves erode and undercut rock to make steep slopes.

• As a sea cliff erodes above the waterline, a bench of rock, called a wave-cut platform, can remain below the waterline.

• sea caves – waves cut holes into weak or fractured rock

• More erosion on sea caves makes sea arches and sea stacks.

What coastal landforms are made by erosion?

• What landforms can you identify in the image below? How did each landform form?




• beach -made up of material deposited by waves and currents.

• The size and shape of materials on a beach depend on how far the material has traveled, the type of material, and how it is eroded.

• sandbar - underwater or exposed ridge of sand, gravel, or shell material.

• barrier island - long, narrow island, (usually made of sand) that forms parallel to the shoreline a short distance offshore.



Living on the Edge – read pg. 39


• Barrier islands are found all over the world.

• Barrier islands can change shape and be eroded away by tides and large storms.

• Barrier island erosion can be slowed down by using sandbags and other anti-erosion techniques.

8 grade the dynamic earth (module e) · 2020. 1. 9. · what landforms can streams create? what do...

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